This invention relates to an ultrasonic diagnosing apparatus.
An ultrasonic diagnosing apparatus is adapted to transmit ultrasonic beams toward a to-be-examined subject such as a living body from an ultrasonic probe, constituted of an array of electroacoustic converters, and receive the ultrasonic beams reflected from the region of interest of the living body to obtain living tissue data.
A general method for obtaining a tomographic image of the region of interest of a human being is by sequentially shifting ultrasonic beams from an electroacoustic converter array in a direction in which the electroacoustic converters are arranged, brightness-modulating electron beams in a CRT by an electric signal corresponding to the ultrasonic beam reflected from the region of the humam being and received by the electroacoustic converters, and making the sequential shift of the ultrasonic beams synchronous with a scanning line shift by the electron beams in CRT to display a tomographic image of the living body region on the CRT. Such a display mode is called a B-mode display and is disclosed in, for example, U.S. Pat. No. 3,881,466. A method for obtaining such sequentially shifted ultrasonic beams with electronic control is called as an electronic linear scan method and disclosed in, for example, U.S. Pat. No. 3,919,683. According to the B-mode method only one tomographic image is obtained which corresponds to one cross sectional region of the living body. Therefore, where any affected area of the human being is to be examined, it is necessary to beforehand locate any possible affected area of the human being by palpation, X-ray examination, etc. and examine its neighboring areas by observing a B-mode image obtained. Where the certified engineer performs such an operation, a plurality of B-mode images are obtained at an interval of, for example, 5 mm. Later, the doctor diagnoses an affected region of the living body on the basis of the B-mode images taken. With such a method, however, it is impossible to reduce the inter-cross-section spacing between adjacent B-mode images of the area of the living body to less than a certain extent. For this reason, it is difficult to obtain data for each significant inter-cross-section of the area of the living body. Furthermore, there is a fear that a living body may be jerked during examination and, in such a case, the inter-cross-section spacings of the area of the living body are often irregularly tomographed. Since the living body is moved to a considerable extent due to a heart beat and respiration, there is a great risk of erroneous diagonsis. For group diagnosis or mass-screening in particular, it is required that examination be completed in a brief period, and even in this case detailed data needs to be obtained.
In FIG. 1 is shown one of most recent ultrasonic diagnosing apparatus for "group diagnosis", as recently reported on an article of lecture, page 49--The 28th meeting of Japan Society of ultrasonics in medicine--in which an ultrasonic probe is moved in a direction vertical to the scanning surface of a living body. As will be evident from FIG. 1, a total of 26 seconds is required to scan 9 cross-section areas of the living body, since 2 seconds is taken for scanning one cross-section and 1 second is required for the probe to be moved to the next cross-section. During the scanning it is desirable, though difficult, that respiration be halted. A movement of 40 mm at maximum is effected to obtain 9 cross-sectional images and in this case the width at which the scanning is effected is narrow.
Japanese Patent Bulletin 21580/1964 discloses a method for obtaining a plane image on a plane which is a predetermined distance below the surface of a subject to be examined. In this method, however, it is impossible to obtain cross-sectional images of varying depth.